Apparatuses incorporating memory card reading devices such as payment terminals include many securing devices and implement methods for ensuring that the apparatuses are employed in compliance with the use for which they are planned and that they comply with security standards laid down by certification organizations.
For example, in the field of payment terminals for payment cards, the manufacturers have developed solutions for protecting the multi-layered electronic printed circuit board or boards (PCBs) of the payment terminals.
More specifically, a printed circuit board is a carrier, generally a plate, used to electrically connect a set of electronic components to one another in order to obtain a complex electronic circuit. This plate consists of an assembly of several fine layers of copper separated by an insulating material. The layers of copper are etched by a chemical method to obtain a set of tracks terminated by chips. The printed circuit board is often coated with a layer of colored varnish (prepreg+FR4) which protects the tracks from oxidation and possible short circuits. The tracks electrically connect different zones of the printed circuit. The chips, once perforated, set up an electrical link either between the soldered components through the printed circuit board or between the different layers of copper (this is the so-called “via” technique). In certain cases, the non-perforated chips are used to solder surface-mounted components.
Unfortunately, deterioration has been observed in multi-layered electronic printed circuit boards. This deterioration takes the form of piercing, scraping or any other intrusive technique aimed at shorting, cutting, snooping, etc. a printed circuit board.
For example, a deterioration may correspond to the cutting of a track of the printed circuit of a payment terminal in order to annihilate the dispatch of information aimed at triggering the “attack” mode of the secured processor of a payment terminal.
In order to protect the multi-layered electronic printed circuit, protection solutions have been developed.
A first protection consists in introducing a sort of wire mesh with activation on electrical levels. These are fine adjacent tracks covering the entire part to be protected. For example, one track can be connected to VCC and the other to GND. Any piercing of this wire mesh can result in the cutting of one or other of the links, which would be detected. It could even result in shorting between two tracks, which would also be detected. Numerous variations of this device can be used. The detection can be done on voltage levels or on the compliance of the signals travelling through these tracks.
A second protection consists in introducing a wire mesh similar to that of the first solution described here above and comparing the voltage characteristics of a signal sent at one end of the mesh with the characteristics of a signal received at the other end.
The drawback of these solutions lies in the fact that there is a space, however tiny it may be, between the different tracks. This enables a possible shorting or again piercing without activation on an electrical level or again without modification of the characteristics of the signal received at the end of the wire mesh as compared with the characteristics of the signal sent at another end.
Thus, to date, the inventors have not identified any already existing simple solution for providing efficient protection to a multi-layered electronic printed circuit board against any intrusion by malicious third parties.